Crossflow pressure liquid filtration with ultrasonic enhancement

ABSTRACT

Methods and apparatus for increasing the duration of uninterrupted filtering flow by using crossflow filtration and ultrasonic energy with in difficult to filter process liquids (e.g. of the kind having (1) a carrier liquid, (2) coalescing solids particles which tend to adhere and bridge filter element gaps sized substantially larger than such particles, and (3) larger impurity elements to be filtered out of such process liquid and sized larger than such filter element gaps).

FIELD OF THE INVENTION

This invention relates generally to crossflow industrial liquid pressurefilter apparatus and methods, particularly for process liquids of thekind having (1) a carrier liquid, (2) coalescing solids particles whichtend to stick together to bridge and thus blind a filter element gapwhich is sized larger than the width of such particles, and (3) largerimpurity elements to be filtered out and which are sized larger thansuch a filter element gap.

BACKGROUND OF THE INVENTION

Ultrasonic energy has been applied to prior flow separation situationsbut, insofar as known to Applicants, not to crossflow filtration ofliquids in the above mentioned field.

The Assignee of the present invention has developed, over time, filtersystems for difficult to filter liquids, such as liquid solutions,suspensions and the like having a high solids content, particularlycertain liquids of a viscous nature or otherwise having a high solidscontent such as colloidal gels, mineral and clay slurries, starchsolutions, petroleum oil products and the like, in which the solids tendto coagulate or coalesce, wherein the filtering out of large impurityelements is a difficult problem.

Such problem was early recognized in, for example, Petter, et al. U.S.Pat. No. 3,161,159, assigned to the Assignee of the present invention.

Subsequent Davis U.S. Pat. No. 5,198,111; Davis et al. U.S. Pat. No.5,527,462 and Vander Ark U.S. Pat. No. 5,569,383, all assigned to theAssignee of the present invention, require, (per housing) a single,relatively large diameter, cylindrical filter element which uses barrierfiltration flow from inside out. A cleaning member moves along the inletsurface of the filter element to mechanically wipe or scrape solids fromthe filter element gaps back into suspension in the liquid to befiltered.

Later DeKock et al. U.S. Pat. No. 6,395,186 provides such awiper/scraper, barrier type, filter unit, in which plural ultrasonictransducers are spaced axially and circumferentially on the outside ofthe filter housing to assist barrier filtration of composite liquidsincluding particularly aggressively coalescing solids particles, whichwould otherwise quickly blind the filter element at a commerciallyunacceptable rate.

The above discussed filter systems use barrier-type filtrationprocesses, wherein all of the incoming process liquid must pass throughthe filter element to be stripped of unwanted relatively large impurityelements, namely those size of larger than the filter element gaps.

Further, each of the prior filter systems above discussed, has, within agiven filter housing, only one or perhaps up to three, filter elements,and hence a relatively low area of filtration material (e.g. screen) perfilter housing.

In a continuing effort to improve efficiency in filtering difficultliquids, particularly of the kind above discussed, Applicants have foundthat in certain situations, all of the process liquid, going to a userprocess, need not be filtered (e.g. in certain oil refinery processes).Moreover, Applicants have found that there is often very little spaceavailable for filtration equipment in a given liquid processinstallation, so as to make desirable the maximizing of filter mediaarea while minimizing the outside dimensions of the filter housing.

Accordingly, the objects and purposes of the invention include provisionof methods and apparatus for filtration, commercially acceptable flowrates and flow durations, using crossflow filtration and ultrasonicenergy for preventing bridging of filter element gaps, without need formechanical wiping/scraping, for difficult to filter process liquids(e.g. of the kind having (1) a carrier liquid, (2) coalescing solidsparticles which tend to stick together to bridge and thus blind a filterelement gap sized larger than the width of such particles, and (3)larger impurity elements to be filtered out of such process liquid andsized larger than such a filter element gap).

SUMMARY OF THE INVENTION

This invention includes methods and apparatus for increasing theduration of uninterrupted filtering flow by using crossflow filtrationand ultrasonic energy with in difficult to filter process liquids (e.g.of the kind having (1) a carrier liquid, (2) coalescing solids particleswhich tend to adhere and bridge filter element gaps sized substantiallylarger than such particles, and (3) larger impurity elements to befiltered out of such process liquid and sized larger than such filterelement gaps).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a filter system embodying the presentinvention.

FIG. 1A shows a modification of the FIG. 1 system.

FIG. 2 is an enlarged fragmentary, central cross sectional view of thetop portion of the FIG. 1 filter unit.

FIG. 3 is similar to FIG. 2 but of the bottom portion of the FIG. 1filter unit.

FIG. 3A is an enlarged fragment of FIG. 3.

FIG. 4 is an enlarged fragment of FIG. 2.

FIG. 5 is an enlarged fragment of FIG. 4.

FIG. 6 is a schematic pictorial view of a conventional piezoelectrictransducer core usable in the FIG. 1 apparatus.

FIGS. 7A, B, C and D schematically illustrate interactions, underdiffering conditions, of solids in the feed liquid with holes/gaps in afilter element wall.

FIG. 8 is a pictorial view of the cage shown in fragmentary form in FIG.2.

FIG. 9 is an enlarged sectional view substantially taken on the lineIX-IX of FIG. 2.

FIG. 10 is an enlarged sectional view substantially taken on the lineX-X of FIG. 2.

FIG. 11 is an enlarged sectional view substantially taken on the lineXI-XI of FIG. 2.

FIG. 12 is an enlarged sectional view substantially taken on the lineXII-XII of FIG. 3.

DETAILED DESCRIPTION

A process liquid filtration system 16 (FIG. 1), embodying the presentinvention, includes a crossflow process liquid filter unit 18. Thefilter unit 18 includes an elongated, generally cylindrically shaped,filter housing 20 having a process liquid (feed) inlet port 30 and aprocess liquid (retentate) outlet port 26. The filter unit 18 alsoincludes a filtered liquid outlet port 44.

The inlet port 30 is at the near upper portion of the housing 20(FIG. 1) and is adapted to receive incoming feed liquid to be filtered.The inlet port 30 may be conventionally formed, e.g. here by a stub pipe34 which opens to and extends radially from the housing 20.

The system 16 (FIG. 1) may be installed in parallel with a conventionalprocess feed liquid user apparatus FEU fed by a pump PU from a processliquid tank TK, in turn fed from any convenient source SO of processfeed liquid.

The feed pump PU (FIG. 1) also feeds process liquid from the tank TKthrough a strainer ST and a normally open inlet valve IV into the inletport 30.

A major part of the feed liquid, propelled by the pump PU into thehousing 20, simply passes unfiltered through the filter housing 20 in acrossflow manner, and exits through the retentate outlet 26 and anormally open retentate outlet valve ROV, preferably through a flowcontrol FC2, back to the tank TK. The control FC2 here shown is of aconventional type, wherein a flow sensor FS outputs a signal (e.g.electrical) through a feedback loop controller FLC and feedback loop FLto vary the opening of a flow rate control valve FCV.

The filtered liquid (filtrate) outlet port 44 (FIG. 1) may beconventionally formed, e.g. here by a relatively small diameter stubpipe 41 which opens to and extends radially from the top portion of thefilter unit 18. The filtrate outlet port 44 connects through a normallyopen filtrate outlet valve FOV and a further flow control FC3 to anydesired filtrate user apparatus FUA. The control FC3 may be a modelCamflex II-style control valve, commercially available from DresserMasoneilan located at Dresser, Inc. Valve Division, 85 Bodwell Street,Avon, Mass. 02322-1190 USA. The control FC2 is conveniently similar tocontrol FC3.

The aforesaid liquid connections to the ports 30, 26 and 44 may be byany conventional means, for example conventional respective flanges 30,24 and 42, as seen in FIG. 1.

A first pressure sensor PS1 senses liquid pressure in the retentateoutlet line, here between the retentate outlet valve ROV and the flowcontrol FC2. Similarly, a second pressure sensor PS2 samples liquidpressure in the line between the filtrate outlet 44 and the filtrateoutlet valve FOV. The pressure sensors PS1 and PS2 output signals,corresponding to the pressure in their respective liquid lines, to adifferential pressure responsive control DP which provides a controloutput to the filtrate outlet valve FOV to close same, when the liquidpressure at the retentate outlet 26 (and hence the unfiltered liquidportion of the filter unit 18) sufficiently exceeds the liquid pressureat the filtrate outlet 44.

The filter housing 20 (FIGS. 2 and 3) comprises a generally cylindricalperipheral wall 51. The housing peripheral wall 51 has an interior face57. If desired, the housing peripheral wall 51 may be formed bycoaxially welding together a top, flanged portion 52, an elongatecentral tubular portion 53, a downwardly narrowing, or bell, portion 54and a bottom flange portion 55, all of generally annular construction.The bottom flange portion 55, at its bottom end, incorporates theradially outward extending retentate outlet flange 24. The top flangeportion 52 at its upper end incorporates a radially outwardly extendingtop flange 60.

The filter unit 18 (FIGS. 2 and 4) includes a filtrate manifold 70 whichcoaxially overlies the housing top flange 60. The filtrate manifold 70has a coaxial central throughbore 76. The filtrate manifold 70 comprisesa radially extending, substantially disc-like central body 71 andcoaxial central outboard and inboard bosses 72 and 73, respectivelyextending axially upward and downward (in FIG. 2) from the radiallyextended central body 71.

The filter housing 20 has an elongate central chamber 56circumferentially surrounded by the housing peripheral wall 51. Theinboard boss 73 is of outer diameter to fit snugly, but axiallyslideably, in the upper end of the elongate central chamber 56 of thefilter housing 20.

The filtrate manifold central body 71 is coaxially fixedly butreleasably connected to the flange 60 of the filter housing, in anyconventional manner, such as by a coaxial, circular array ofcircumferentially spaced nut/bolt fasteners (not shown), through thecoaxial flange 60 and manifold body 71. The axis 75 of one such nut/boltfastener is schematically indicated in FIG. 2 for purposes ofillustration. Such firmly, axially and sealingly sandwiches an annularseal 74 between the flange 60 and manifold body 71.

A coaxial, annular channel 80, here substantially rectangular in crosssection, opens downward from the central inboard boss 73 and is radiallyspaced between the interior face 57 of the housing peripheral wall 51and the central bore 76 of the filtrate manifold 70.

A filtrate outlet passage 81 (FIG. 2) is substantially L-shaped in crosssection. The passage 81 extends axially upward from communication withthe annular channel 80 and then bends radially outward in the centralbody 71 to open through the peripheral wall 82 of the manifold centralbody 71. A recess 83 in the radially outer end of the outward passage 81may snugly, fixedly, and sealingly receive the inboard end of a stubpipe 84 carrying the flange 42 (FIG. 1) and defining a portion of thefilter liquid outlet port 44.

A plate-like ring 90 (FIG. 2) is coaxial with, and recessed in, thebottom portion of the annular recess 80 and is fixed therein by anyconvenient means such as welding. A circumferential array of holes 91opens vertically through the ring 90, in radially spaced relationbetween the inner and outer edges of the ring 90. The holes 91 arepreferably evenly circumferentially spaced around the ring 90. In theembodiment shown, the holes 91 are threaded.

An adapter fitting 100 (FIGS. 2, 4, 9 and 10) is coaxially, releasably,fixedly received in and depends from each of the holes 91 of the ring 90so as to provide an array of circumferentially spaced adapter fittings100. Such array, the ring 90, and the annular channel 80 are preferablycoaxial with the housing peripheral wall 51 and are spaced inboardtherefrom, as indicated in FIGS. 2 and 4.

In the embodiment shown, the adapter fittings 100 (FIG. 5) each comprisean upper, mounting sleeve 101, a lower, compression nut 102, and anaxially interposed compressible ring 103.

The upper portion of the mounting sleeve 101 is externally threaded at104 (FIG. 5) and threads into the internally threaded hole 91 in thering 90. The mounting sleeve 101 has a coaxial throughbore 105, thelower portion of which is recessed at 106 so as to define a downwardfacing annular step 107. The mounting sleeve 101 has a generallycylindrical, reduced diameter, externally threaded, lower end portion109 and an axial midportion 108 of external shape (e.g. hexagonal)engagable by a tool (e.g. wrench) for tightening or loosening themounting sleeve 101 with respect to the ring 90.

Each compression nut 102 has a bottom wall 118 and an annular peripheralwall 119 upstanding from the bottom wall 118. The interior face of theperipheral wall 119 has a threaded upper portion 120 to thread onto theexternal threads 109 of the lower portion of the mounting sleeve 101.The lower portion 121 of the interior face of the recess 106 ispreferably downwardly and outwardly tapered to the bottom end 110 of themounting sleeve 101. The bottom wall 118 of the compression nut 102 hasa coaxial bore 122 of diameter equal to or slightly larger than therecess 106 of the mounting sleeve 101.

For each adaptor fitting 100, a corresponding, elongate tubular elementadapter 130 (FIGS. 2 and 5) has an upper portion loosely encircled bythe nut 102 and snugly but slidably carrying the compression ring 103.Above the compression ring 103, the element adaptor 130 is snugly butslidably received in the recess 106 of the mounting sleeve 101. The topend 131 of the element adapter 130 abuts the downward facing step 107 atthe top of the recess 106.

Upon threading the nut 102 upwardly on the mounting sleeve 101, thebottom wall 118 of the nut 102 axially compresses the compression ring103 against the tapered portion 121 at the bottom end 110 of themounting sleeve 101 and so expands radially the cross section of thecompression ring 103 forceably and sealingly between and against thetapered portion 121 of the mounting sleeve 101 and the outer peripheralsurface of the element adapter 130. This fixedly and sealingly dependsthe element adapter 130 from the adapter fitting 100, and hence from theplate-like ring 90 and filtrate manifold 70.

To facilitate threaded tightening on the mounting sleeve 101, the nut102 may be provided with a tool (e.g. wrench) engagable outer peripheralsurface shape, e.g. a hexagonal shape as indicated at 123 in FIG. 2.

The adapter fitting 100 may be similar in broad principle to a domesticsink drain compression fitting. One suitable adapter fitting 100 iscommercially available as P/N 810-1-8B7 Bore Thru Male Connector,{fraction (1/2)} inch″ Tube to {fraction (1/2)} inch NPT Male, availablefrom Swagelok Company of 29500 Solon Road, Solon, Ohio 44139 USA.

The element adapters 130 (FIG. 2) extend downward past the inlet port30, and thus are located in the incoming flow impingement zone. Eachelement adapter 130 is generally funnel shaped, with a widened,generally bell shaped lower end portion 132. The lower end portion 132preferably comprises an enlarged diameter, downward opening, cylindricalrecess 133 joined by a generally bell shaped, diameter reducer passage134 to the bottom of the reduced diameter, major length portion of theelement adapter 130.

A plurality of elongate, preferably cylindrical, perforate filterelements 140 (FIG. 2) coaxially depend from corresponding ones of theelement adapters 130. Thus, each recess 133 snugly fixedly receives theupper end portion of a coaxial filter element 140. The filter element140 is fixed within the cylindrical recess 133 by any convenient means,such as welding. In the embodiment shown, the reducer passage 134 makesroughly a 3:1 reduction in diameter, from the outer diameter of thefilter element 142 to the inside diameter of the major portion 135 ofthe element adapter 130. The peripheral wall of the reducer passage ispreferably smoothly and sinuously curved in cross section, as seen inFIG. 2, to smoothly, and with minimum turbulence, channel filteredliquid from the interior of the filter element 140 upward through theelement adapter 130 and into the annular channel 80 of the filtratemanifold 70. While dimensions may vary from unit to unit, in theparticular unit shown in FIG. 2, the lower portion 132 of the elementadapter comprises about 15-20% of the total length of the elementadapter.

The filter element 140 is, as shown in FIGS. 2 and 3, of relativelysmall diameter and relatively great axial length. For example, given afilter element 140 of one inch outside diameter, its length may be inthe range of three to six feet. These slim elongate filter elements 140are sometimes graphically referred to as “sticks”. Typically, the filterelement 140 comprises a cylinder 141 of metal mesh material with itsbottom end portion (FIG. 3) snugly received in, closed by and stiffenedby a cup-like closure 142 (FIG. 3A) fixed thereto, as by soldering in aconventional manner. The filter element 140 extends down to a locationadjacent the bottom bell portion 54 of the filter housing 20. The filterelement 140 is preferably of stainless steel, but other materials arecontemplated.

In this way, an array of axially extending, circumferentially spacedelement adapters 130 and filter elements 140 may depend from andcommunicate with the plate-like ring 90 and filtrate manifold 70.

In one unit constructed in accord with the invention, eight filterelement/element adapter units 140/130 were provided in a singlecircumferential array generally coaxial with the filter housing 20.However, it is contemplated that such a circumferential array maycontain more (or fewer) filter element/element adapter units 140/130.Moreover, it is contemplated that, by suitably expanding the diameter ofthe filter unit 18, two or more such circumferential arrays may dependin loosely telescoped, radially spaced, coaxial relation within thefilter housing 20, and communicate through respective correspondingcoaxial annular channels (not shown, but similar to and spaced outboardfrom the annular channel 80 of FIG. 2) with the filtrate outlet passage81, so as to accommodate a substantially higher number (e.g. 100) offilter elements 140 in a single filter unit 18.

The filter unit 18 further includes an ultrasonicfiltration/regeneration enhancer unit 160 (FIGS. 1 and 2). The enhancerunit 160 comprises an elongate cylindrical resonator tube 162 coaxiallysurmounted by an ultrasonic transducer 163. The transducer 163 isenergized by a conventional ultrasonic power supply UPS (FIG. 1) toapply ultrasonic energy to the resonator tube 162. A mounting flange 164(FIG. 2) extends radially from an intermediate portion of the resonatortube 162 for fixing the enhancer unit 160 with respect to the manifold70. In the embodiment shown, a circumferential array of threaded studs165 extend coaxially upwardly from the outboard boss 72 of the filtratemanifold 70 and passes through a corresponding circumferential array ofholes 166 in the mounting flange 164. Nuts 167, threaded on the upperends of the studs 165, are tightened to clamp the mounting flange 164fixedly and coaxially atop the filtrate manifold 70. A conventionalannular seal ring 180 is here axially clamped between the mountingflange 164 and filtrate manifold 70 to prevent liquid leakage radiallyoutward therebetween.

The seal rings 74 and 180 here shown may be of a conventional kindhaving outer peripheral edges notched to fit around respective mountingbolts 75 or studs 165.

The resonator tube 162 (FIG. 2) extends coaxially downwardly, in aradial clearance manner through the central bore 76 of the filtratemanifold 70, and downward coaxially loosely within the circumferentialarray of element adapters 130 and filter elements 140. The bottom of theresonator tube 162 is closed by a resonator plug 168 (FIG. 3) ofselected mass and fixed therein by any convenient means such as welding.

Units comprising generally similar resonator tubes and ultrasonictransducers have been used for a variety of purposes, but not, insofaras Applicants are aware, in pressure liquid filters, particularly of thetype to which this invention is directed. More particularly, such unitsare available in various lengths for operation at a desired frequency ina predetermined range. Units of this general kind are availablecommercially from Telsonic Ultrasonics Inc. located at Bridgeport, N.J.with e.g. models MRG-20-1400 and RS-20-48-12F being available. In theembodiment shown, the transducer includes a piezoelectric driver coupledto the top of the resonator tube 162 to apply, at a selected ultrasonicfrequency (e.g. 20 kHz), mechanical shock waves to the top of theresonator tube 162. The shock waves travel the length of the resonatortube 162 and reflect back up the tube from the resonator plug 168 at thefar end of the resonator tube 162. As a result, the resonator tubeaxially extends and contracts, by a minute amount, at the appliedultrasonic frequency. That results in a corresponding minute contractionand expansion of the diameter, and circumference, of the resonator tube162, generally in the manner of a rubber band or bungee cord, whereinlengthwise stretching reduces diameter/circumference and lengthwisecontraction diameter/circumference.

The resonator plug 168 (FIG. 3) acts as a counterweight that is tuned tothe frequency of the ultrasonic pulses applied to the resonator tube 162by the transducer 163. Thus, tuning the transducer 163 and resonatortube 162 to the same desired frequency, and applying ultrasonic pulsesfrom the transducer 163 to the resonator tube 162, may be said to causethe resonator tube 162 to ring like a bell (though inaudibly). Theultrasonic vibration of the resonator tube 162 is substantially uniformalong its entire length and hence along substantially the entire lengthof the surrounding filter elements 140. Thus, the ultrasonic energyapplied to the filter elements is substantially free of hot spots at oneor more points along the length thereof.

Moreover, the cost of the inventive filter system is minimized at leastin part by the requirement for only a single ultrasonic transducer toserve the entire filter housing and all of the filter elements therein.Moreover, the cost of the filter housing is kept low by avoiding anyneed for mounting plural ultrasonic transducers on the peripheral wallthereof.

FIG. 6 schematically shows a conventional ultrasonic transducer core189, wherein a screw 194 threads into a central tapped hole (not shown)in the outboard portion of a cylindrical driver slug 204. The head 193of the screw 194 presses an axial stack of annular elements 195, 192,202, 196, 198 and 190 against the driver slug 204. In the embodimentshown, the stack comprises, in sequence, washers 195, a massive annularback slug 192, an annular ceramic insulator 202, an annular conductiveterminal plate 196, an annular piezoelectric disk 197, and a furtherannular conductive terminal plate 190. The center holes in thepiezoelectric disk 197 and outboard terminal plate 196 are larger indiameter than the shank of the screw 194 to prevent electrical contactof the screw 194 with the piezoelectric disk and terminal plate 196.Insulated electrical conductors 199 and 200 connect the transducer core198 to the ultrasonic power supply UPS in FIG. 1.

It will be recognized that, given a transducer 163 having a coregenerally like that in FIG. 6, the driver slug 201 may be coaxiallyaligned with (and e.g. partially extend into) the upper end of theresonator tube 162 and be fixed therein by any convenient means. Also,the size of parts, for example the mass of the back slug 192, would beselected to correspond to the desired resonant frequency of vibration ofthe resonator tube 162 and ultrasonic power supply UPS.

Advantageously, the present invention locates the ultrasonic transducer163 outside, and indeed in spaced relation to, the filter housing. Thus,a hot feed liquid moving through the filter housing does not tend toheat up the transducer 163. This is advantageous because heat applied toa piezoelectric element in an ultrasonic transducer tends to cause sameto lose efficiency (produce less ultrasonic output for the sameelectrical input). Indeed, a transducer 163 spaced from the filterhousing, could, if desired, easily be wrapped in cooling jacket or thelike.

While the elongate resonator member 162 is here provided in the form ofa tube, it is contemplated that other forms (e./g. a solid bar) ofelongate resonator member might be employed.

Preferably, structure is provided to prevent the bottoms of the filterelements 140 and resonator tube 162 from moving laterally with respectto each other and to the filter housing 20, to protect the filterelements from possible damaging contact with the upper end portion ofthe housing 20 during installation or removal of the filter elements 140and resonator tube 162 with respect to the housing 20, and to maintainthe filter elements 140 and resonator tube 162 in generally fixedrelative relation for movement as a unit to a location outside thefilter housing 20. Such structure would also prevent contact betweenresonator tube 162 and filter elements 140 that could cause variation inthe ultrasonic system frequency and power output. In the preferredembodiment shown, such structure conveniently takes the form of a cage220 (FIG. 8) comprising an upper hoop 221, and a lower spider 222axially spaced therefrom and connected thereto by axially extending,circumferentially spaced guard members 223. In essence, the cage 220surrounds and extends along the filter elements 140 and resonator tube162. The hoop 221 and spider 222 here are conveniently each cut fromplate stock, but may otherwise be formed as desired.

The hoop 221 (FIGS. 2 and 8) is axially located between the adapterfittings 100 and feed liquid port 30 and the spider 222 (FIG. 3) ispreferably located at the bottom of the filter elements 140 andresonator tube 162.

The hoop 221 (FIGS. 8 and 11) here comprises a generally ring shapedbody 230 from which radially inwardly protrude evenly circumferentiallyspaced adapter receiving loops 231 and radially outwardly protrude guardmember receiving loops 232. Each adapter receiving loop 231 has an axialthroughhole which snugly but slidably receives axially therethrough acorresponding one of the element adapters 130. The guard memberreceiving loops 232 each have an axial throughhole which fixedly (as bywelding) receives the upper end of the corresponding guard member 223.

The spider 222 (FIGS. 8 and 12) comprises a disk-like hub 240, a rim 241and circumferentially spaced spokes 242 extending radially outward fromthe hub 240 fixedly to the rim 241 to fix the rim in coaxial surroundingrelation with the hub. Axial flow openings 243 extend through the spider222. The flow openings 243 are radially bounded by the hub 240 and rim241 and circumferentially bounded by adjacent ones of the spokes 242.

The rim 241 includes closely circumferentially spaced, axial openings244. In the embodiment shown, the rim 241 somewhat less than fullyencloses the openings 244, so that the openings 244 are formed asradially outward opening, undercut recesses. The openings 244 snugly,but axially removably, receive the corresponding closed bottom portions,here defined by the cup-like closures 142, of corresponding filterelements 140. The rim 241 further includes radially outwardlyprotruding, guard member receiving, loops 251 which are evenly spacedcircumferentially between the openings 244. The loops 251 have axialthroughholes fixedly (as by welding) receiving the lower end portions ofcorresponding ones of the guard members 232.

The hub 240 has an upward facing surface for abutting the slug 168 atthe lower end of the resonator tube 162 (FIG. 3). A screw 252 extendsupward through a central hole 253 in the hub 240 and threadedly engagesthe resonator plug 168, to releasably fixedly coaxially secure thebottom of the resonator tube 162 atop the hub 240 of the spider 222.

Thus, the cage 220 is fixed by the screw 253 through the hub 242 to theresonator plug 168 at the bottom of the resonator tube 162, thecup-like, bottom portions of the filter elements 140 seat in theopenings 244 of the spider 222, the spider fixedly connects via theupstanding, rod-like guard members 223 to the hoop 221 whose radiallyinboard loops 231 receive the element adapters 130 upwardlytherethrough.

The outboard loops 232 and 251 extend radially outwardly beyond thefilter elements 140, such that the loops 232 and 251 and the rod-likeguard members 232 lie radially outboard of the filter elements 140 andthus provide a cage of protection around such filter elements. Thespider openings 244 and inboard hoop loops 231 laterally locate thefilter elements 140 and their element adapters 130 in substantiallyfixed relation. The guard members 223 in the embodiment shown, areelongate rods, stepped adjacent their ends to axially abut the hoop 221and spider 222, with reduced diameter end portions extending through theloops 232 and 251.

Thus, the manifold 70, and ultrasonic unit 160, adapter fittings 100,element adapters 130, filter elements 140, and cage 220 form a cartridge260 insertable or removable, as a unit, with respect to said housing 20and movable as a unit outside the housing 20 from a convenient place ofassembly, or to a convenient place for disassembly.

The above discussed structure is preferably corrosion resistant, and isconveniently formed substantially of stainless steel, although the seals74 and 180 may be of a suitable resilient material. However, thematerials employed may vary depending on the intended application.

To assemble the unit 18 (FIGS. 2 and 3), the mounting sleeves 101 of theadapter fittings 100 are threaded into the holes 91 in the plate-likering 90 fixed to the manifold 70. The upper end portions of the elementadapters 130 (with their filter elements 140 coaxially attached) areinserted through the corresponding loops 231 in the hoop 221 and thecup-like, bottom closures 142 of the filter elements 140 are droppedinto their openings 244 (FIGS. 8 and 12) of the assembled cage 220. Thecompression nuts 102 and compressible rings 103 are slid over the topsof the corresponding element adapters 130. The upper end of each elementadapter 130 is then slid into the corresponding recess 106 (FIG. 6) ofits corresponding adapter mounting sleeve 101. Nut 102 is threaded ontosuch mounting sleeve 101 and tightened to fix the element adapter 130,and thus its depending filter element 140, to the filtrate manifold 70.

The resonator tube 162 of the assembled enhancer unit 160 is theninserted coaxially through the seal ring 180 and the central bore 76 ofthe filtrate manifold 70 and the array of element adapters 130 andfilter elements 140, until the mounting flange 164 drops over the studs165 and onto the annular seal 180, and the resonator plug 168 bottoms onthe cage hub 240, to which it is then fixed by the screw 252. Themounting flange 164 is then fixedly pressed against the seal 180 by thenuts 167. The parts thus assembled form a self supporting cartridge 260.The annular seal 74 is then coaxially placed atop the housing top flange60 and the cartridge 260 is lowered coaxially into the filter housing20. With the central body 71 of the filtrate manifold 70 resting on theseal 74 on the housing top flange 60, same are then fixed sealingly andcoaxially together, as by conventional nut/bolt units (the center lineof one of which is indicated at 75 in FIG. 2).

Installation of thus assembled filter unit 18 is then completed bymaking its connections to the liquid and electrical circuitry abovediscussed with respect to FIG. 1.

Reversal of the above sequence allows, e.g. should it be desired after aperiod of use, quick and easy removal of the cartridge 260 (includingthe cage 220, filtrate manifold 70, filter elements 140, elementadapters 130, adapter fittings 100, and the entire ultrasonic enhancerunit 160 from the filter housing 20. After such removal it is a simplemanner to disassemble the cartridge 260, e.g. to inspect and/or repairor replace parts thereof.

Operation

With the filter unit 18 connected as shown in FIG. 1, unfiltered processliquid (feed liquid) is pumped from the tank TK through pump PU,strainer ST, inlet valve IV and into the inlet port 30. The feed liquidradially enters the filter housing 20 and impinges on the slim,intermediate portions of the element adapters 130 (FIG. 2). Thus,radially inwardly directed feed flow is spaced above the filter elements140, such that no part of the perforate wall of the filter elements 140is hit by radially directed, incoming, feed flow. This avoids immediateblinding or damage to the upper portion of the adjacent filter elements140, and avoids differences in filtering characteristics along thelength of the filter elements 140.

The incoming feed liquid flow from the inlet port 30, as indicated bythe arrows in FIG. 2, turns and flows downwardly along the elementadapters 130, smoothly past the substantially bell shaped lower endportions thereof and thence down along, and parallel to the filteringface of each of the elongate filter elements 140. The feed liquid flowcontinues downwardly past the bottom of the filter elements 140 (FIG. 3)and then out through the bell portion 54 and flange portion 55 of thefilter housing 20. Filtration is of crossflow, not barrier, type.

Thus a major, unfiltered portion of the feed liquid (termed theretentate) flows from the bottom of the filter housing 20, through theretentate outlet valve ROV (FIG. 1) and flow control FC2, and back intothe tank TK.

As hereafter discussed, the remaining portion of the feed liquid,incoming through the inlet port 30, passes through the walls of thefilter elements 140 (FIG. 2) and (as filtrate) passes in the directionof the upwardly directed arrows through the open upper ends of thefilter elements 140, the tubular element adapters 130, the fittings 100,the annular channel 80 of the filtrate manifold 70, and then laterallyoutward through the filter outlet passage 81 and the stub pipe 84 of thefiltrate liquid outlet port 44. Such filtrate liquid then passes throughthe filtrate outlet valve FOV and flow control SC3 to any desiredfiltrate user FUA.

During such crossflow filtration, typically 5 to 10% of the incomingfeed liquid entering the inlet port 30 emerges from the filtrate outletport 44 as filtrate usable by the filtrate user FUA. For example, in anoil refinery the feed liquid may be relatively low grade oilcontaminated with relatively large impurity elements and which thus haslimited, relatively low value usage. On the other hand, the filtrate isstripped of such relatively large impurity elements and thus is acleaner oil, substantially improved in its value, for example byanywhere from a dollar or two per barrel to multiple dollars per barrel,depending on the particular filtrate user FUA involved. For example,filtrate suitable to be processed into gasoline may experience asubstantial (e.g. $30 per barrel) improvement in value. Thus, flowing5,000 gallons of feed liquid per hour through the filter housing 20, toyield 100 gallons per hour of filtrate, worth $2/barrel more than theincoming feed liquid, is a commercially desirable achievement.

If the filter unit 18 cleans, and outputs as filtrate, 5-10% of theincoming feed liquid, then clearly the unfiltered portion of the feedliquid (the retentate), emerging from the bottom of the filter unit 18and returned to the tank TK, has an increased concentration ofrelatively large contaminate elements. However, such retentate may beusable by certain process feed users FEU. Indeed, for some feed liquids,it may actually be advantageous to build up the concentration of thelarger impurity elements in the retentate. For example, in the oilrefinery business those larger impurity elements, in sufficientconcentration, are themselves a saleable product (as in asphalt for roadbuilding). Thus, a filter system embodying the invention can efficientlycontribute to the production of two saleable products, one from theretentate and the other from the filtrate.

Attempts to pass, by barrier mode filtration, all incoming feed liquidof the mentioned difficult, high solids kind through a filter element,to separate the large impurities therefrom, have tended to unacceptablyquickly (almost instantaneously for some feed liquids) blind thefiltration element and terminate filtration in a commerciallyunacceptable manner. The present invention solves the problem ofproviding commercially acceptable filtration of such difficult feedliquids by combination of crossflow filtration and ultrasonicenhancement of filtration and regeneration.

Under the present invention, crossflow filtering continuously routesincoming feed liquid along the length of the filter elements. Thecontinuous flow of feed liquid over the inlet face of each filterelement tends to wash away accumulating solids, such that a modestpercentage of the feed flow, stripped of impurities larger than thepores of the filter wall, continuously emerges from the filter unit, asfiltrate, for a longer period of time before blinding of the filterelement wall occurs and filtrate production stops.

As schematically seen in FIG. 7A, it is desirable in crossflowfiltration that the carrier liquid CL, with relatively large impurityelements IE to be filtered out, flow along the input side of theperforate filter element wall 141, while a portion of the carrier liquidCL, together with relatively smaller entrained solids particles CP, i.e.smaller than the filter element pores 143, passes through the pores 143in the filter element wall 141, as filtrate.

Over time, as indicated in FIG. 7B, a porous cake of larger impurityelements IE may build up on the filter element wall 141. However, theporosity of the relatively thin layer of cake in FIG. 7B still allowssolids particles CP smaller than the filter wall pores 143, togetherwith a portion of the carrier liquid CL, to pass through the filter wall141 as filtrate. To allow formation of a desired thickness of porouscake on the inlet surface of the filter elements 140, the filterelements preferably are spaced from each other by something more thantwice the desired cake thickness. In one unit constructed according tothe invention, wherein a {fraction (3/16)} inch cake thickness was founddesirable, the spacing of the inlet faces of adjacent filter elements140 exceeded twice that ({fraction (3/8)} inch) and was approximately{fraction (1/2)} inch, although it is contemplated that these distancesmay vary depending on the desired cake thickness for the particularapplication in which the filter unit is to be used. On the other hand,since cake does not form on the resonator tube 162, the adjacent inletsurfaces of the filter elements 140 are preferably closer to theresonator tube than to each other. The object is that a given filterelement be spaced from adjacent filter elements and from the resonatortube (1) distantly enough to allow formation of the desired thickness ofcake on the filter elements, without contact by cake on one filterelement with either cake on an adjacent filter element or with theresonator tube 162, but (2) closely enough that all feed liquid flowingthrough the filter housing moves rapidly and closely along the inletfaces of the filter elements to enhance its cake limiting cleaningeffect on the filter elements. The foregoing spacing from the resonatortube 162 of course applies to the inner circle of filter elements, thatimmediately surround the resonator tube 162, since filter elements ofsurrounding circles (if any) are disposed outside that inner circle andremote from the resonator tube 162. Eventually, filter cake may furtherbuild up on the input side of the filter wall 141 sufficient to slowfiltrate production and thereby require regeneration of the filter unit,but for commercial acceptance regeneration should be needed infrequentlyand be brief.

However, in certain difficult, high solids liquids, the small particlesCP, intended to pass through the filter element wall 141, are of a typewhich readily stick together, or coalesce, and so tend to quickly adheretogether on the input side of the filter wall 141 and blind the pores143 therein, as schematically shown in FIG. 7C. Indeed, such sticky,coalescing, small particles CP may quickly bind together larger impurityelements IE and so quickly form a cake impenetrable by the carrierliquid and desirable small particles CP, on the input side of the filterwall 141 as schematically shown in FIG. 7D, such that the filter elementbecomes inoperative and filtration ceases.

Applicants have found that, even in crossflow filtration, the presenceof such sticky, coalescing particles CP may blind the filter morequickly than is commercially acceptable. However, Applicants have foundthat the energization of the transducer 163 of the ultrasonic enhancer160 (FIG. 1), and the resulting (at ultrasonic frequency) radialexpansion and contraction of the resonator tube 162 along its length, inthe feed liquid surrounding the filter elements 140, disrupts animpenetrable (as in FIGS. 7C and 7D) build up of cake on the input sideof the filter wall 141, so that any cake that may build up remainsrelatively thin and porous (as in FIG. 7B) and a blinding, impenetrablebuild up of cake schematically shown (as in FIGS. 7C and 7D is avoidedat least for a substantially longer, commercially acceptable time. It isbelieved that the ultrasonic agitation of the feed liquid by theenergized resonator tube 162 may limit undesirable, impenetrable cakebuild up, at least in part by preventing bridging (as schematicallyshown in FIG. 7C) of the pores 143 in the filter element wall 141 by thesmall, sticky, coalescing particles CP.

Thus, filter cake on the input face of the filter elements 140 is, underthe present invention, continually attacked by two mechanisms, namely(1) the washing effect of the feed liquid crossflow along the filterelement wall and (2) the dispersive effect caused by a continuousultrasonic cavitation.

Ultrasonic energy, in the present invention, has two beneficial effects:(1) the disruption of solids caked on the filter element wall so thatthey may be more easily washed away by the crossflow current of the feedliquid and (2) the disruption of small coalescing particles bridging theholes in the filter element wall which allows these particles to passthrough the filter element wall, rather than being trapped in the filtercake. The net effect is to delay an eventual rise of differentialpressure across the cake and filter element wall, due to filter cakegrowing and becoming non-porous.

Thus, the combination of crossflow filter operation and ultrasonicenergization of the elongate resonator tube 162 along the length of thefilter elements 140 has been found by Applicants to allow continuousfiltration operation indefinitely, or at least for a much longer,commercially acceptable, period of time, before output of filtrate isimpeded.

Given a sufficient build up of filter cake on the input side of thefilter elements 140, pressure sensors PS1 and PS2 (FIG. 1) sense adifference in pressure sufficient to cause the differential pressureresponsive control DP to close the filtrate outlet valve. Thus, filtrateoutflow of the filtrate-outlet 44 stops and the pressure differentialacross the filter element walls 141 (the pressure differential betweenthe pressure sensors PS1 and PS2) disappears. Thus, the liquid pressureholding the cake against the input side of the filter wall 141disappears, such that there is nothing (except for the relatively minorcohesive force of the sticky, cohesive, small particles CP) to hold thefilter cake to the inlet side of the filter element wall 141. Thus, theagitation of the feed liquid by the energized resonator tube 162 helpsto break up the filter cake, while the continuing flow of feed liquidwashes away dislodged portions of the cake out the retentate outlet 26and so back to the tank TK. This regenerates the filter elements 140 totheir original clean state.

This regeneration, under the present invention, is short in duration andmay be in the range of seconds e.g. 30 seconds. The differentialpressure responsive control DP is conveniently set to reopen thefiltrate outlet valve FOV after a preselected, sufficient regenerationtime to restore normal filtering operation and output of filtrate to thefiltrate user FUA. The differential pressure responsive control DP isconveniently of conventional type, and indeed of the type usedcommercially for a number of years in controlling regeneration in priorproduction filter systems of the Assignee of the present invention. Anexample is disclosed in U.S. Pat. No. 5,792,373 assigned to the Assigneeof the present invention.

Over the duration of the regeneration cycle, the feed flow through thefilter housing and the application of ultrasonic energy are bothcontinued. In view of the closed filtrate outlet valve FOV and resultingabsence of differential pressure holding filter cake to the inlet wallof the filter element, the cake is readily washed from the inlet face ofthe filter element. Since the filter element is a single layersurface-retention element, the level of solids on the filter elementinput face is kept low, as there is no depth filter media to entrap suchsolids.

The inventive system herein disclosed, has been found in testing toprovide at least a 100% improvement in filtration performance overcorresponding prior barrier filtration technology. As one advantage,this allows a filtration system according to the present invention to besized much more economically, and still achieve the same performance asin prior systems.

Indeed, it appears that systems according to the present invention mightprovide as much as 2½ times the performance of a comparable barrierfiltration system, i.e. 2½ times the gallons of filtrate produced persquare foot of surface area of filter element per unit time. Thestandard of comparison in a barrier mode filter is the REACTOGARD®filtration system which has been marketed for several years by, and iscovered by aforementioned U.S. Pat. No. 5,792,373 of the Assignee of thepresent invention.

The performance of the filtration system according to the presentinvention is further enhanced by provision of the flow control FC3 inthe filtrate outlet line from the filtrate outlet 44 to the filtrateuser FUA. The flow control FC3 allows careful control of the filtrateoutflow rate. By limiting the rate of filtrate outflow with the flowcontrol FC3, the formation of cake on the inlet side-of the filterelement wall 141 is slowed, and it is believed that any cake beingformed is less dense and thus less inhibits flow through the filterelement wall. Absent the flow control FC3, the filtrate flow rateessentially self-regulates by building cake on the filter element wall,which may result in premature blinding of the filter element. Moreparticularly, the constant filtrate draw rate maintained by the filtrateflow control FC3 prevents the perforate wall of the filter element fromimmediately blinding by a rush of feed through the clean filter elementperforate wall.

The ability of the present invention to maintain long periods offiltration, with at most brief, infrequent regeneration times, clearlyavoids the need to shut off process liquid (feed) flow through thefilter housing 20 for filter element cleaning. It also avoids the needto disassemble the filter unit for withdrawal, external cleaning, andreplacement of filter elements on a regular basis, which would causesubstantial economic losses in process downtime and extra labor costs.

Additionally, the present invention avoids the need for backwashing offilter elements and so eliminates considerable expense. In particular,providing a backwash supply is expensive, either because of use forbackwashing of liquid that has already been filtered or the need toprovide a different backwash liquid. Additional expense results from theneed for additional tanks and pumps and a destination for dirty backwashliquid.

While one unit according to the invention employed ultrasonic energy at20 kiloHertz (kHz) frequency, differing frequencies are contemplatedwhich for example might include frequencies up to and beyond 30 kHz.

Also, in one unit according to the invention, about 1,000 watts ofultrasonic energy was applied to the ultrasonic enhancer unit 163,although power levels in the range 500 to 2000 watts are contemplated.

Applicants have found it desirable, in accord with the invention, tominimize the space laterally around the resonator tube 162 and filterelements 140, so as to maximize the velocity of feed liquid lengthwiseof the input face of the filter elements 140, to help wash away filtercake from the input face of the filter elements.

In accord with the invention, the pores 143 in the walls of the filterelements 140 are sized in the so-called microfiltration range whichincludes pore sizes down to about 0.5 micron. In contrast, priorcrossflow filtration has conventionally been, insofar as Applicants areaware, (1) used in the so-called ultrafiltration range and below, inwhich filter membrane pores are sized an order, or more, of magnitudesmaller than 0.5 micron, and (2) not used on liquids of the kind ofinterest here.

Moreover, prior conventional thinking appears to have been thatmicrofiltration could be satisfactorily conducted using existing barriermode type filters. However, Applicant has found that, with somedifficult, high solids liquids having particularly gummy, sticky,coalescing solids particles to be maintained in the filtrate, it isdifficult to obtain commercially acceptably long periods ofuninterrupted filtration using barrier filtration technology.

Several advantageous features of the present invention are summarized asfollows.

The present invention is applicable to multiple filter housings, eachcontaining at least 8 to 100 high-aspect ratio (high length to diameterratio), elongate (e.g. 0.30 to 72 inches long) filter elements. Fineretention (e.g 10 micron and smaller), single layer mesh filterelements, which can be classified as true “surface retention” filterelements, are preferably employed. The inventive filter system isoperated as a crossflow filter, with a minority percentage of the totalfeed being filtered and drawn off as filtrate, while a majoritypercentage of the feed flows along the inlet face of the filter elementwall and assists in the removal therefrom of captured solids (i.e. thefilter cake). While in crossflow filtration mode, ultrasonicenergization assists in maintaining porous any filter cake being formed.While in regeneration mode, ultrasonic energization aids in the removalof the filter cake once it has grown to the critical cake thickness (asmeasured by differential pressure). The flow control FC3 utilizesfeedback control to maintain constant filtrate flow rate from the filterhousing. The system is particularly useful in handling feed having highsolids loading (in excess of 1500 parts per million (PPM)) by weight(and perhaps a multiple of that) with particle size distributiontypically less than 30 micron diameter but with significantconcentrations of particulate (at least 10% by mass/volume) finer thanthe rated media retention (hole size in the filter element wall). Thefilter elements are regenerated in-situ the filter housing bycombination of the washing effects of the crossflow feed stream andultrasonic dispersion from the integrated ultrasonic transducer. Theregeneration cycle is controlled by closing the filtrate outlet(isolation) valve FOV over the duration required for regenerating thefilter elements.

FIG. 1A shows a modification of the FIG. 1 system. The FIG. 1A system ispreferably similar to the above described FIG. 1 system except asfollows.

The FIG. 1 tank TK is optional and may not be possible in some customerapplications. Thus, in the FIG. 1A system, the filter housing 20 takesfeed liquid directly from the process liquid source SO. Thus, in FIG.1A, the process feed liquid source SO outputs through a line L to theprocess feed user FEU and through the open inlet valve IV to the inletport 30. A suitable restriction sufficient to divert the desired flowfrom line L to line L1 is interposed in the line L downstream of the L1.For the embodiment shown, such restriction comprises a conventionalfeedback flow control FC1, like the above-described control FC2,comprises a flow sensor FS which outputs a signal through a feed backloop controller FLC and feedback loop FL to control flow through a flowcontrol valve FCV. In FIG. 1A, the flow sensor FS of the flow controlFC1 is interposed in a branch line L1 between the process feed line Land the inlet valve IV, and the valve FCV is interposed in the line Ldownstream of the branch line L1. The control FC1 is appropriately sizedto the desired process feed flow in line L and may be of the samegeneral type as above-described control FC2, or may be a similarconventional control supplied by the customer in whose plant the systemis installed.

In the FIG. 1A system, the FIG. 1 control FC2 is not needed and so isomitted, the retentate outlet valve ROV being connected to the processfeed line L downstream of the flow control valve FCV of the control FC1to flow retentate from the filter unit to the process feed user FEU.

The valves IV and ROV may be manually controlled, or controlled by asuitable, conventional remote or programmable controller (not shown), inwhich case it may be desired to interpose normally open manual valvesMV1 and MV2 adjacent the line L, respectively in the branch line L1 anddownstream of the retentate outlet valve ROV. The valves MV1 and MV2 maybe closed to allow disconnection of the filter unit from the processfeed line L.

Although particular preferred embodiments of the invention have beendisclosed in detail for illustrative purposes, it will be recognizedthat variations or modifications of the disclosed apparatus, includingthe rearrangement of parts, lie within the scope of the presentinvention.

1. A method of increasing the productive duration of filtering, in apressure liquid filter unit, of feed liquid including a carrier liquidand coalescing solids bits which tend to stick together and thus blind afilter element gap, comprising: crossflowing feed liquid along an inletface of a filter element disposed in a filter housing and therebywashing at least portions of said solids bits from said inlet face,while ultrasonically driving a member extending along said filterelement inlet face and thereby reducing the ability of solids bits tostick to said inlet face; passing a portion of said feed liquid throughsaid filter element and out of said filter housing as filtrate with atleast larger solids bits removed; passing the remainder of said feedliquid beyond said filter elements and expelling same from said filterhousing as retentate.
 2. The apparatus of claim 1 including passingfiltrate liquid having a solids/liquid ratio less than that of said feedliquid toward a filtrate user, and passing retentate having asolids/liquid ratio increased from that of said feed liquid to aretentate user.
 3. The method of claim 2 in which said filtrate andretenate are respectively lighter and heavier fractions, than said feedliquid, of feed oil in an oil refining circuit.
 4. The method of claim 1including feeding retentate from a filter housing into a feed liquidsystem and supplying feed liquid from said feed liquid system to a feedliquid inlet of said filter housing for continuous liquid circulationthrough said feed liquid inlet, past said filter elements, and, asretentate, back into said feed liquid system, and also feeding feedliquid from said feed liquid system to a feed liquid user device.
 5. Afilter apparatus for feed liquid including a carrier liquid andcoalescing solids bits which tend to stick together and thus blind afilter element gap, the apparatus comprising: a filter housing; plural,elongate filter elements in said filter housing; an elongate,ultrasonically driven member located inside said filter housing andextending along said filter elements; a filtrate outlet adjacent one endof said filter housing, a given said filter element having a filtrationwall with an inlet face and a filtrate outlet path to said filtrateoutlet; a feed liquid inlet and retentate outlet adjacent opposite endsof, and defining a cross flow feed liquid path along said filterelements and ultrasonically driven member; said filter apparatus havingfiltration and regeneration states combining: (1) an open condition ofsaid crossflow feed liquid path, and (2) ultrasonic energization of saidultrasonically driven member, and distinguished from each other by anopen filtrate liquid flow condition through said filtrate outlet pathand filtrate outlet in said filtration state versus a closed filtrationflow outlet in said regeneration state.
 6. The apparatus of claim 5including an ultrasonic driver drivingly coupled to said ultrasonicallydriven member, said ultrasonic driver being fixed outside said filterhousing and being substantially independent of the temperature of theinterior of said filter housing.
 7. A filter apparatus for feed liquidincluding a carrier liquid and coalescing solids bits which tend tostick together and thus blind a filter element gap, the apparatuscomprising: a filter housing; plural, elongate filter elements in saidfilter housing; an elongate, ultrasonically driven member located insidesaid filter housing and extending along said filter elements, saidfilter elements comprising elongate, hollow, tubular elements, a givensaid filter element having a filtering wall in an outer face andsurrounding an interior filtrate liquid passage; a feed liquid inlet anda retentate outlet for a majority of feed liquid entering said feedliquid inlet, said feed liquid inlet and retentate outlet being axiallyspaced on said filter housing and located adjacent opposite ends of saidfilter elements and defining a crossflow feed liquid path endwise ofsaid filter housing and along outer faces of said filter elements andultrasonically driven member; a filtrate outlet for a minor portion offeed liquid entering said feed liquid inlet, said filtrate outlet beingadjacent said filter housing and remote from said retentate outlet andcommunicating with said filtrate liquid passage of a given filterelement; a filtrate liquid path from said filtrate outlet andconnectable to a filtrate user device; a flow limiting control in saidfiltrate liquid path whereby to avoid blinding of a given filter elementby an initial uncontrolled rush of feed liquid through said filterelement wall.
 8. The apparatus of claim 7 including pressure sensorsadjacent said retentate outlet and feed liquid inlet, a filtrate liquidvalve in series with said filtrate outlet and a corresponding saidpressure sensor, a differential pressure control with an input partcoupled to said pressure sensors and an output part coupled to saidfiltrate liquid valve and responsive to a preselected pressuredifferential between said retentate outlet and filtrate liquid outlet toclose said filtrate liquid valve and thereby initiate regeneration ofsaid filter elements.
 9. The apparatus of claim 7 in which said filtrateoutlet has a filtrate outlet valve, said filter apparatus has afiltration operating state and a regeneration operating state, saidfiltration operating state corresponding to an open condition of saidfiltrate outlet valve and an open flow condition through said feedliquid inlet and retentate outlet, said regeneration operating statecorresponding to a closed condition of said filtrate outlet valve and acontinued open flow condition through said filtered liquid inlet andretentate outlet.
 10. The apparatus of claim 7 including a feed liquidsystem and a feed liquid loop from said feed liquid system through saidfeed liquid inlet and retentate outlet of said filter housing back tosaid feed liquid system, a path from said feed liquid system connectableto a feed liquid user device, a path from said filtrate liquid outletconnectable to a filtrate liquid user device.
 11. The apparatus of claim10 including second and third flow limiting controls in said feed liquidloop and respectively adjacent said feed liquid inlet and retentateoutlet.
 12. A filter apparatus for feed liquid including a carrierliquid and coalescing solids bits which tend to stick together and thusblind a filter element gap, the apparatus comprising: a filter housing;plural, elongate filter elements in said filter housing; an ultrasonicdriver fixed outside said filter housing; an elongate ultrasonicallydriven member arranged in ultrasonically driven relation with saiddriver, located inside said filter housing, and extending along saidfilter elements.
 13. The apparatus of claim 12 in which saidultrasonically driven member is surrounded by said filter elements andextends in the length direction of said filter housing and in which saidfilter housing has an end and an elongate peripheral wall, saidultrasonic driver being fixed substantially coaxially with respect tosaid filter housing adjacent said end and extending away from said end,said ultrasonically driven member extending coaxially of said ultrasonicdriver and lengthwise of said filter housing and being spaced from theinside of said peripheral wall.
 14. The apparatus of claim 13 in which asingle ultrasonic driver and ultrasonically driven member are associatedwith said filter housing and said plural filter elements in said filterhousing.
 15. The apparatus of claim 12 in which said filter housing hasa heated feed liquid inlet port, said ultrasonic driver being spacedfrom said filter housing and thus substantially free of heating by feedliquid in said filter housing.
 16. The apparatus of claim 12 in which agiven filter element has a tubular filtering wall, an inlet face on theoutside of said wall, an outlet face on the inside of said wall, saidultrasonically driven member extending along and adjacent said inletface.
 17. The apparatus of claim 16 in which plural ones of said filterelements surround said ultrasonically driven member in close spaced,substantially parallel relation, and in which the lateral spacing ofsaid filter elements from each other and from said ultrasonically drivenmember is substantially less than the radius of said filter elements andultrasonically driven member, so as to enhance the velocity of feedliquid along the inlet face of a given said filter element.
 18. A filterapparatus, comprising: an elongate filter housing having a liquid inletand outlet spaced longitudinally of said filter housing, said filterhousing having a peripheral wall; an array of elongate filter elementsin said filter housing; an elongate ultrasonically driven member in saidfilter housing, inserted in said array of filter elements, said filterelements and ultrasonically driven member extending longitudinally insaid filter housing, said array of filter elements and saidultrasonically driven member being fixed together to form an assemblyremovable from and replaceable in said filter housing as a unit.
 19. Theapparatus of claim 18 including a cage surrounding and extending alongsaid filter elements and ultrasonically driven member, said cagecomprising a first end member adjacent said inlet and a second endmember adjacent said outlet and plural longitudinal guard membersconnecting said first and second end members, said first end member (1)being located adjacent one end of said filter elements and surroundingat least a major circumferential portion of said ultrasonically drivenmember and (2) laterally locating said filter elements with respect tosaid ultrasonic driven member and filter housing peripheral wall, saidsecond end member (1) being located adjacent the other end of saidfilter elements and (2) laterally locating said filter elements withrespect to said ultrasonically driven member and filter housingperipheral wall.
 20. The apparatus of claim 19 in which saidlongitudinal guard members are spaced in a circumferential array ofoutside diameter exceeding the outside diameter of said array of filterelements.
 21. The apparatus of claim 20 in which said assembly includessaid cage, said cage being in substantially fixed relation with saidfilter elements and ultrasonically driven member, said cage including acircumferential array of surfaces more closely opposing the peripheralwall of said filter housing than the radially outermost surfaces of saidfilter elements and ultrasonically driven member, such that said cageprotects said filter elements during inserting and withdrawing saidcartridge with respect to said filter housing.
 22. The apparatus ofclaim 18 wherein said assembly comprises a cage extending lengthwise ofsaid filter elements and fixed with respect to end portions of saidfilter elements remote from said inlet.
 23. The apparatus of claim 18 inwhich said filter elements and ultrasonically driven member arereleasably fixed in said assembly for easy replacement with saidcartridge outside said filter housing.
 24. The apparatus of claim 18including elongate element adapters extending past said inlet, saidassembly including a generally hoop shaped member having inner,circumferentially spaced openings receiving said adapters therethroughin radial and circumferential located relation, said generally hoopshaped member having a portion outboard of said openings and closelyradially opposing an interior surface of said filter housing.
 25. Theapparatus of claim 18 including a spider-like member located adjacentthe ends of said filter elements nearest said filter housing outlet andincluding: (1) a hub portion fixed to an adjacent end of saidultrasonically driven member, (2) a rim portion spaced outboard of saidhub portion and having circumferentially spaced receivers receivingadjacent end portions of said filter elements, and (3) circumferentiallyspaced spoke-like elements coupling said hub portion and rim portion andcircumferentially spaced from each other by axial flow openings throughsaid spider-like member.
 26. The apparatus of claim 18 in which saidassembly includes relatively fixed, elongate, circumferentially spaced,bar-like members extending substantially axially along and at leastpartly radially outward of said filter elements and facing an interiorperipheral wall of said filter housing in filter element protectingrelation.
 27. A filter apparatus, comprising: a filter unit having ends,a filtrate outlet adjacent one said filter unit end and a feed liquidinlet spaced between said ends, said filter unit including a filterhousing, said feed liquid inlet defining a generally lateral feed liquidinflow path, opening generally laterally into a feed liquid zone in saidfilter unit; plural, generally tubular filter elements in said filterhousing, a given said filter element having an exterior face exposed tosaid feed liquid zone in said filter housing and an interior facebounding a filtrate chamber in said given filter element, said filterelements being spaced between said feed liquid inlet and said secondfilter unit end, said filter elements being located out of saidgenerally lateral feed liquid inflow path; plural, elongate, generallytubular adapters, a given said adapter extending endwise from a givensaid filter element past said feed liquid inlet and being coupled tosaid filtrate outlet.
 28. The apparatus of claim 27 including anelongate ultrasonic resonator in said housing and extending along saidfilter elements and opposing said exterior faces of said filterelements, said housing having a retentate outlet, said feed liquid inletand retentate outlet being adjacent opposite ends of said filterelements and defining a path for unfiltered feed liquid in said housingalong said filter elements and ultrasonic resonator.
 29. The apparatusof claim 27 in which said filter unit includes a manifold closing oneend of said filter housing and connecting between the correspondingfilter element filtrate chamber and said filtrate outlet, said manifoldhaving an annular channel open toward said filter elements throughcorresponding holes, said adapters being aligned with said holes andreleasably fixedly coupled to said manifold.
 30. The apparatus of claim22 including a manifold having an annular channel open toward saidfilter elements, a ring fixedly closing the inboard end of said annularchannel, said ring having plural, circumferentially spaced holes, pluraltubular compression fittings, a given said compression fitting beingthreaded into a corresponding one of said holes and being sleeved on acorresponding said tubular adapter.
 31. The apparatus of claim 27 inwhich, in the region of said lateral feed liquid inflow path, saidtubular adapters are laterally more widely spaced than said filterelements to minimize resistance to feed liquid flow into said housingand maximize even lateral distribution of feed liquid among said filterelements, said tubular adapters being of less diameter than said filterelements, a given adapter having a widened end fixed to the adjacent endof its corresponding filter element.
 32. The apparatus of claim 22including structure spaced between ends of said filter housing in radialand circumferential displacement limiting relation with said filterelements, said structure protectively surrounding said plural filterelements.